\section{Conclusion}\label{sec:conclusion}
3D IC is a promising solution for performance improvement. However, the fabrication cost is the major hinder for designers to adapt 3D designs. In this paper, a 3D design cost-driven optimization flow is proposed to find the cost-efficient designs in 2D and 3D cases. Both TSV and interposer-based 3D structures are considered. The cost-efficient designs are found with balanced area utilization and metal layers. The experiment results show that for both 2D and 3D cases, metal layer reduction and optimal area utilization exploration can achieve cost saving compared to baseline designs. We can achieve cost saving up to 19\% for TSV-based 3D designs,
and 26\% for interposer-based 3D designs, respectively, compared to the baseline designs.